Clustering and Lagrangian Statistics of Bubbles

Due to their relevance and occurrence in both natural phenomena and in industrial applications, the study and understanding of bubbly flows is currently an important topic for fluid dynamicists. Bubble columns are commonly used in bio- and petrochemical industries to enhance mixing, mass and heat transfer. In these systems, the bubbles are the only energy input as there is no flow a priori. Bubble columns are also referred to as pseudo-turbulence because the bubbles induce liquid fluctuations in the originally quiescent liquid. These disturbances are the result of the hydrodynamic interactions among the bubbles and their heterogenous distribution. Turbulent flows transporting particles are ubiquitous in nature, being of such relevance in diverse fields ranging from atmospheric physics to oceanography. Usually the convected particles have a different density and size than the transporting fluid, turbulent bubbly flows are a particular case of them. In recent years, Lagrangian studies—i.e. studies following the particle motion—of particles in turbulence have gained considerable attention because this approach is closer to the inherent mixing and transport characteristic of turbulence. Yet there is still the challenge and interest to comprehend more the Lagrangian statistics of particles in turbulence. This work studies bubbly flows in two different flow conditions. In the first part, we study the pseudo-turbulence induced by rising bubbles in quiescent liquid. In the second part, we study the Lagrangian statistics and clustering of micro-bubbles in homogeneous isotropic turbulence.